The present invention relates to a concealed transmitter unit and receiver units in speakers to be used in a stereo audio equipment which comprises a concealed transmitter unit installed in a center speaker to transmit audio signal, and two receiver units installed in two rear speakers to receive transmitted signals from the concealed transmitter center speaker. The present invention system uses wireless technology to transmit audio signal to the receiving speakers in order to eliminate the limitation and inconvenience of external electrical devices thus further elevates the maximum performance and application of an audio equipment.
The ideas of the present invention was generated from the popular use of home theater set and stereo audio equipment. The conventional stereo audio equipment usually comprises of one stereo surround processing amplifier, two left and right sound track center speakers, one center low bass speaker and two left and right sound tract rear speakers together to provide sound effects like that of cinema house or theater. However, to install a set of conventional stereo audio equipment, a lot of external complicated electrical devices is required to connect all speakers to the main sound source or player. Sometimes the length of electrical devices limits users to think where and how the audio equipment can be perfectly allocated so to suit the family internal concept and gives its best performance. Moreover, the exposed electrical devices creates burden on maintenance and cleanness. If to keep the electric wires from sight, the installation cost of the audio equipment will be high. The biggest problem with conventional wired audio equipment is that it confines users to a particular place where the equipment is located in order to listen to the music of the equipment. However, when users leave the place and still want the sound of equipment to be heard, it is necessary to turn the volume louder. Situations like this may therefore cause interference and disturbance to others.
The present invention has been accomplished to provide a wireless concealed transmitter stereo center speaker system which eliminates the aforesaid problems. It is one object of the present invention to provide a wireless concealed transmitter and receivers installed in the center and rear speakers so that sound signal of the audio player can be transmitted to the rear speakers for output wirelessly. It is another object of the present invention to provide a wireless concealed transmitter and receivers in center and rear speakers which can be installed everywhere easily without the limitation and confinement of electrical devices. It also gives users the freedom to adjust the volume of any individual speaker, so that the users can listen to the music of the audio equipment without interfering other persons. It is still another object of the present invention to provide a wireless concealed transmitter stereo center speaker system which eliminates the use of complicated matching devices by using an inductance type transmitting antenna which reduces the floating of frequency so to provide stable audio signal and not to be interfered by walls, glasses, ceilings or pillars. It is still another object of the present invention to provide a wireless concealed transmitter stereo center speaker system which consumes low working voltage. It is still another object of the present invention to provide a wireless concealed transmitter stereo center speaker system which automatically cuts off external alternating or battery power supply when the audio equipment does not work, so that it is very energy saving. It is still another object of the present invention to provide a wireless concealed transmitter stereo center speaker system which adopts an external and internal dual adjustable oscillatory frequency regulating circuit for the transmitter unit as well as the receiver units so that the range of the frequency can be broadly adjusted. It is still another object of the present invention which provides an adjustable xe2x80x9cexternal frequency controller VR1xe2x80x9d to enable the users (consumers) to change the frequency of the first local oscillation and broaden the frequency range. It is necessary to elaborate the mechanism of the xe2x80x9cFrequency Controller VR1xe2x80x9d in the present invention. In the external and internal dual adjustable oscillatory frequency regulating circuit the Frequency Controller VR1 is used as a potential divider. The moment users turn the tuner to adjust the Frequency Controller VR1 the center output electrical level fluctuates and varies with the adjusting of the tuner. The VCO (variable capacitor diode) is being controlled by R31 and R5, hence they induce the DR to vary its oscillation meanwhile Q1 also varies its oscillatory frequency. The Frequency Controller VR1 is capable of controlling the VCO variant range approximately from +/xe2x88x920.5 MHz to +/xe2x88x922 MHz. Internally, technicians can control the VCA and VCB to broaden frequency range to +/xe2x88x923 MHz. Therefore the capacity of transmitting frequency variation is far better than the conventional use of SAW. Meanwhile technicians can also replace VCA and VCB to fixed capacitors in order to fix the frequency. On the other hand, in the receiver unit the Frequency Controller VR1 is used as a potential divider as well. When users turn the tuner to adjust the Frequency controller VR1, the center electrical level output varies. Now the VCD is being controlled by R11 and R10 to induce the DR varies its oscillation and further results in the oscillatory frequency of Q1. In this way the Frequency Controller VR1 is capable of controlling VCO""s variation approximately from +/xe2x88x920.5 MHz to +/xe2x88x923 MHz. Likewise, technicians can broaden the frequency range by controlling the VCA and VCB to approximately +/xe2x88x925 MHz or more. Hence the capacity of receiving frequency variation is better than that of using a SAW method. Meanwhile the first local oscillation in the VCO is approximately 1003 MHz after mixing with external transmitting frequency (eg. 912 MHz) the resulting first IF is about 91 MHz. Please refer to FIGS. 1 and 2. Technicians can also replace the VCA and VCB to fixed capacitors if a fixed first down-convert is desired.
According to the preferred embodiment of the present invention, the concealed transmitter unit in the center speaker comprises an automatic audio level regulating circuit to regulate the audio level of the output signal of an audio equipment to a predetermined range, a power control circuit controlled by the output signal of the audio equipment to provide the necessary working voltage, and an inductance antenna to transmit output signal from the concealed transmitter center speaker to the receiver units of rear speakers. The receiver unit comprises an automatic 24-time frequency divider circuit to effectively discriminate left and right sound tracks, and an auto-shut off circuit to automatically cut off power supply from either external alternating current source or battery supply when the audio equipment does not work. Furthermore, the transmitter unit and the receiver unit further use a respective (external and internal) dual adjustable oscillatory frequency regulating circuit consisting of an oscillatory transistor, a dielectric resonator, and a variable capacitor and a variable capacitor diode for regulating the range of the frequency.